Touch panel sensor, touch panel device and display device

ABSTRACT

A touch panel sensor includes a substrate and an electrode having a detection electrode and an extraction electrode connected to a detection electrode. The electrode, in any cross-section thereof in the thickness direction, includes a metal layer which occupies at least part of the cross-section. The metal layer of the detection electrode and the metal layer of the extraction electrode are formed integrally at a joint between the detection electrode and the extraction electrode. The detection electrode includes a conductive mesh having conductive wire arranged in a mesh pattern, the conductive wire having a height of not less than 0.2 μm and not more than 2 μm and a width of not less than 1 μm and not more than 5 μm. The conductive wire of the conductive mesh each have a base surface on the substrate side, and a flat top surface located opposite to the base surface.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a touch panel sensor having electrodes,and more particularly to a touch panel sensor whose electrodes have alow resistance and has thinned conductive wires. The present inventionalso relates to a touch panel device including the touch panel sensor,and to a display device including the touch panel sensor or the touchpanel device.

Description of Related Art

These days touch panel devices are widely used as input means. A touchpanel device includes a touch panel sensor, a control circuit fordetecting a touch position on the touch panel sensor, wiring and an FPC(flexible printed circuit) substrate. In many cases, a touch paneldevice is used, together with an image display mechanism, as an inputmeans for a variety of devices (e.g. a ticket vending machine, an ATMdevice, a mobile phone, a gaming device, etc.) into which the imagedisplay mechanism such as a liquid crystal display or a plasma displayis incorporated. In such a device, a touch panel sensor is disposed onthe display surface of the image display mechanism; the touch paneldevice enables direct input to a display device. An area of the touchpanel sensor which faces the display area of the image display mechanismis made transparent. The transparent area of the touch panel sensorconstitutes an active area capable of detecting a contact position(approaching position).

Touch panel devices can be classified into various types based on theprinciple of detecting a contact position (approaching position) on atouch panel sensor. A capacitive-coupled touch panel device is currentlyattracting attention because of its optical brightness, good design,easy structure, excellent function, etc. In a capacitive-coupled touchpanel device, a parasitic capacitance is newly produced when an externalconductor (typically a finger) whose position is to be detected comesinto contact with (approaches) a touch panel sensor via a dielectricbody. The touch panel device utilizes a change in the capacitance todetect the position of the external conductor on the touch panel sensor.

The touch panel sensor usually includes a substrate and electrodesprovided on the substrate. The electrodes include detection electrodeslocated in an active area and extraction electrodes located in anon-active area. In many touch panel sensors, detection electrodes aredisposed at positions facing the display area of an image displaymechanism, as disclosed e.g. in JP 2008-98169A, and therefore are formedof a transparent conductive material such as ITO. Such a transparentconductive material has a relatively high refractive index. This canproduce a large difference in light transmittance and light reflectancebetween an area of a touch panel sensor where detection electrodes aredisposed and an area where no detection electrode is disposed. In thecase where there is a large difference in light transmittance and lightreflectance between the two areas, the contour of the detectionelectrodes will be visible to the user of the touch panel sensor, whichis undesirable from the viewpoint of design and, in addition, willsignificantly lower the image quality of the display device.

Another known touch panel sensor uses detection electrodes made of ametal material. The detection electrodes are composed of conductivewires with a narrow width. The active area of the touch panel sensor cantherefore be made to have a sufficiently high light transmittance.Further, because of the high electrical conductivity of the metalmaterial, the surface resistivity (unit: Ω/□) of the touch panel sensorcan be made sufficiently low even when the metal wires each have anarrow width. Such a touch panel sensor is generally produced by firstlaminating a metal foil onto a transparent substrate using an adhesive,and then patterning the metal foil by etching using a photolithographytechnique to form electrodes.

As the image quality of display devices becomes higher and smallportable terminals, called tablets, become widespread these days, thereis a strong demand for the use of thinner electrodes.

However, in the conventional touch panel sensor which uses electrodescomposed of metal wires, the electrodes are produced by etching a metalfoil using a patterned resist as a mask. An industrially-manufacturedmetal foil has a thickness of not less than 10 μm. Metal wires, whichcan be stably produced by etching a metal foil of such a thickness, havea width of at least 10 μm. This is because, as shown in FIG. 21, lateralerosion (side etching) inevitably occurs during etching of the metalfoil, whereby adjacent eroded portions connect with each other below theresist. Once eroded portions connect each other below the resist, thecorresponding portion of the resist cannot be stably supported any more.Consequently, a metal wire formed below the resist portion lacks inlinearity and varies in the height (thickness).

Further, as shown in FIG. 21, the resulting metal wires have atriangular cross-sectional shape projecting from the substrate. Suchmetal wires have a narrow width and a low height, and therefore do nothave a sufficiently high conductivity. Accordingly, the touch panelsensor has a high surface resistivity and thus has a low sensingsensitivity for positional detection. In addition, when such a touchpanel sensor is incorporated into a touch panel device or a displaydevice such that the projecting metal wires face the viewer, the metalwires having a necessary surface resistivity are likely to be visible.Accordingly, a dark/light pattern due to the metal wires of the touchpanel sensor as well as moire due to interference between the metalwires and a pixel array in an image display mechanism, metal wires ofanother touch panel sensor, etc., are likely to be visible.

SUMMARY OF THE INVENTION

Thus, it has not been possible in the prior art to make metal wires,constituting electrodes, sufficiently thin. The present invention hasbeen made in view of such a situation. It is therefore an object of thepresent invention to provide a touch panel sensor whose electrodes havea low resistance and includes thinned conductive wires.

A first touch panel sensor according to the present invention comprises:

a substrate; and an electrode provided on the substrate and having adetection electrode for use in positional detection and an extractionelectrode connected to the detection electrode, wherein the electrode,in any cross-section thereof in a thickness direction, includes a metallayer which occupies at least part of the cross-section, wherein themetal layer of the detection electrode and the metal layer of theextraction electrode are formed integrally at a joint between thedetection electrode and the extraction electrode, wherein the detectionelectrode includes a conductive mesh including a conductive wire whichis arranged in a mesh pattern that defines a large number of open areas,the conductive wire having a height of not less than 0.2 μm and not morethan 2 μm and a width of not less than 1 μm and not more than 5 μm, andwherein the conductive wire of the conductive mesh has a base surface onthe substrate side, a flat top surface located opposite to the basesurface, and a pair of side surfaces extending between the base surfaceand the top surface.

A second touch panel sensor according to the present inventioncomprises: a substrate; and an electrode provided on the substrate andhaving a detection electrode for use in positional detection and anextraction electrode connected to the detection electrode, wherein theelectrode, in any cross-section thereof in a thickness direction,includes a metal layer which occupies at least part of thecross-section, wherein the metal layer of the detection electrode andthe metal layer of the extraction electrode are formed integrally at ajoint between the detection electrode and the extraction electrode,wherein the detection electrode includes a conductive mesh including theconductive wire which is arranged in a mesh pattern that defines a largenumber of open areas, wherein the conductive wire of the conductive meshhas a base surface on the substrate side, a flat top surface locatedopposite to the base surface, and a pair of side surfaces extendingbetween the base surface and the top surface, and wherein a width ofeach conductive wire of the conductive mesh changes such that itdecreases in a direction from the top surface toward the base surface.

A third touch panel sensor according to the present invention comprises:a substrate; and an electrode provided on the substrate and having adetection electrode for use in positional detection and an extractionelectrode connected to the detection electrode, wherein the electrode,in any cross-section thereof in a thickness direction, includes a metallayer which occupies at least part of the cross-section, wherein themetal layer of the detection electrode and the metal layer of theextraction electrode are formed integrally at a joint between thedetection electrode and the extraction electrode, wherein the detectionelectrode includes a conductive mesh including the conductive wire whichis arranged in a mesh pattern that defines a large number of open areas,wherein the conductive wire of the conductive mesh has a base surface onthe substrate side, a flat top surface located opposite to the basesurface, and a pair of side surfaces extending between the base surfaceand the top surface, and wherein a width of the conductive wire of theconductive mesh is narrower at the base surface than at the top surface.

In any of the first to third touch panel sensors according to thepresent invention, the conductive wire of the conductive mesh mayfurther include a blackened layer provided on the opposite side of themetal layer from the substrate and forming the top surface.

In any of the first to third touch panel sensors according to thepresent invention, the conductive wire of the conductive mesh mayfurther include a blackened layer provided on the substrate side of themetal layer and forming the base surface.

In any of the first to third touch panel sensors according to thepresent invention, the width of the conductive wire of the conductivemesh may change such that it solely decreases in a direction from thetop surface toward the base surface.

In any of the first to third touch panel sensors according to thepresent invention, the width of the conductive wire of the conductivemesh may first change such that it solely decreases in a direction fromthe top surface toward the base surface, and then change such that itsolely increases in a direction from the top surface toward the basesurface.

In any of the first to third touch panel sensors according to thepresent invention, the mesh pattern may have a large number of boundarysegments each extending between two branch points, and the boundarysegments define the open areas; and wherein, in the mesh pattern, theaverage of the number of boundary segments extending from each branchpoint may be not less than 3.0 and less than 4.0, and there may exist nodirection in which open areas are arranged at a constant pitch.

In any of the first to third touch panel sensors according to thepresent invention, the mesh pattern may have a large number of boundarysegments each extending between two branch points, and the boundarysegments define the open areas, and, wherein, of the open areascontained in the mesh pattern, those open areas which are surrounded by6 boundary segments may be contained most.

In any of the first to third touch panel sensors according to thepresent invention, the average of the number of boundary segmentsconnected at each branch point may be more than 3.0.

In any of the first to third touch panel sensors according to thepresent invention, the average of the number of boundary segmentsconnected at each branch point may be 3.0.

A touch panel device according to the present invention comprises anyone of the above-described first to third touch panel sensors accordingto the present invention.

A display device according to the present invention comprises any one ofthe above-described first to third touch panel sensors according to thepresent invention or the above-described touch panel device according tothe present invention.

According to the present invention, the conductive wires, constitutingthe electrode of the touch panel sensor, can be thinned whilemaintaining the electrode at a low resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating an embodiment of the present inventionand schematically showing a touch panel device together with an imagedisplay mechanism;

FIG. 2 is a cross-sectional view showing the touch panel device of FIG.1 together with the image display mechanism, the cross-sectionapproximately corresponding to a cross-section along the line II-II ofFIG. 1;

FIG. 3 is a top view showing the touch panel sensor of the touch paneldevice;

FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 3;

FIG. 5 is a diagram illustrating an exemplary mesh pattern in a planview of a conductive mesh 55 contained in the touch panel sensor of FIG.4;

FIG. 6 is an enlarged view of the conductive mesh, illustrating the meshpattern of the conductive mesh;

FIG. 7 is a plan view showing another example of the conductive meshshown in FIG. 5;

FIG. 8 is a graph showing the number of open areas surrounded by avarying number of boundary segments in the conductive mesh of FIG. 7;

FIG. 9 is a diagram illustrating a method for designing the mesh patternof the conductive mesh shown in FIG. 5, the method being to determinebase points;

FIG. 10 is a diagram illustrating a method for designing the meshpattern of the conductive mesh shown in FIG. 5, the method being todetermine base points;

FIG. 11 is a diagram illustrating a method for designing the meshpattern of the conductive mesh shown in FIG. 5, the method being todetermine base points;

FIGS. 12(a) through 12(d) are diagrams showing the determined basepoints in an absolute coordinate system or in a relative coordinatesystem, illustrating the degree of dispersion of the base points;

FIG. 13 is a diagram illustrating a method for designing the meshpattern of the conductive mesh shown in FIG. 5, the method being toprepare a Voronoi diagram from the determined base points and determinethe mesh pattern;

FIGS. 14(a) through 14(e) are diagrams illustrating an exemplary methodfor producing a touch panel sensor;

FIG. 15 is a diagram corresponding to FIG. 2, illustrating a variationof the touch panel device;

FIG. 16 is a diagram corresponding to FIG. 4, illustrating a variationof the touch panel sensor;

FIG. 17 is a diagram corresponding to FIG. 4, illustrating anothervariation of the touch panel sensor;

FIG. 18 is a diagram corresponding to FIG. 3, illustrating yet anothervariation of the touch panel sensor;

FIG. 19 is a diagram corresponding to FIG. 3, illustrating yet anothervariation of the touch panel sensor;

FIG. 20 is a diagram corresponding to FIG. 3, illustrating yet anothervariation of the touch panel sensor;

FIG. 21 is a diagram illustrating a problem in etching of a metal foil;and

FIG. 22 is a scanning electron micrograph of a cross-section of anelectrode.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention will now be describedwith reference to the drawings. In the drawings attached hereto, exceptfor the photograph of FIG. 22, scales, horizontal to verticaldimensional ratios, etc. are exaggeratingly modified from those of thereal things for the sake of illustration and easier understanding.

FIGS. 1 through 14 are diagrams illustrating an embodiment of thepresent invention. In particular, FIG. 1 is a diagram schematicallyshowing a touch panel device together with a display device; FIG. 2 is across-sectional view showing the touch panel device of FIG. 1 togetherwith the display device; FIGS. 3 and 4 are a top view and across-sectional view, respectively, showing the touch panel sensor ofthe touch panel device; and FIG. 5 is a plan view illustrating anexemplary mesh pattern of a conductive mesh provided in the touch panelsensor.

The touch panel device 20 shown in FIGS. 1 through 4 is constructed as aprojection capacitance-coupled touch panel device and configured to becapable of detecting a contact position of an external conductor (e.g. ahuman finger) on the touch panel device. When the capacitance-coupledtouch panel device 20 has an excellent detection sensitivity, it candetect an area of the touch panel device to which an external conductoris approaching. In view of this, the term “contact position” as usedherein includes an approaching position which can be detected withoutactual contact of an external conductor with the position.

<<<Image Display Mechanism 12>>>

As shown in FIGS. 1 and 2, the touch panel device 20 is used incombination with an image display mechanism (e.g. a liquid crystaldisplay device) 12 to constitute a display device 10. The illustratedimage display mechanism 12 is, for example, constructed as a flat paneldisplay, more specifically as a liquid crystal display device. The imagedisplay mechanism 12 includes a liquid crystal display panel 15 having adisplay surface 12 a, a backlight 14 for illuminating the liquid crystaldisplay panel 15 from the back, and a display control section 13connected to the liquid crystal display panel 15. The liquid crystaldisplay panel 15 includes a display area A1 capable of displayingimages, and a non-display area (also called a frame area) disposedoutside the display area A1 such that it surrounds the display area A1.The display control section 13 processes information on an image to bedisplayed and, based on the image information, drives the liquid crystaldisplay panel 15. Based on a control signal from the display controlsection 13, the liquid crystal display panel 15 displays a predeterminedimage on the display surface 12 a. Thus, the image display mechanism 12plays a role as an output device for outputting textual or graphicalinformation in the form of an image.

As shown in FIG. 2, the liquid crystal display panel 15 includes a pairof polarizing plates 16, 18 and a liquid crystal cell 17 disposedbetween the pair of polarizing plates 16, 18. A functional layer 19 isprovided on the light exit side of the polarizing plate 18 disposed onthe light exit side. The functional layer 19 is a layer which isexpected to perform a particular function, and forms the outermost lightexit-side surface, i.e. the display surface 12 a, of the image displaymechanism 12. The functional layer 19 may be, for example, alow-refractive index layer that functions as an antireflection layer (ARlayer). Instead of or in addition to the antireflection layer, thefunctional layer 19 may consist of one or more of an anti-glare layer(AG layer) having an anti-glare function, an abrasion-resistant hardcoat layer (HC layer), an antistatic layer (AS layer) having anantistatic function, etc.

The polarizing plates 16, 18 include polarizers which function toresolve incident light into two orthogonal polarization components, andtransmit one polarization component and absorbs the other polarizationcomponent perpendicular to the one polarization component. In thefollowing description, in order to distinguish between the pair ofpolarizing plates contained in the liquid crystal display panel 15, thelight entrance-side (backlight-side) polarizing plate 16 is referred toas the lower polarizing plate and the light exit-side (viewer-side)polarizing plate 18 is referred to as the upper polarizing plateregardless of the posture of the liquid crystal display panel 15.

The liquid crystal cell 17 includes a pair of support plates and liquidcrystals disposed between the pair of support plates. The liquid crystalcell 17 is configured to be capable of applying an electric field toeach pixel area. When an electric field is applied to a pixel area, thenthe orientation of liquid crystals of the liquid crystal cell 17 changesin the pixel area. For example, a polarization component in a particulardirection (direction parallel to the transmission axis), which haspassed through the lower polarizing plate 16 disposed on the lightentrance side, turns its polarization direction by 90 degrees when itpasses through those pixel areas of the liquid crystal cell 17 to whichan electric field is being applied, whereas the polarization componentmaintains its polarization direction when it passes through those pixelareas of the liquid crystal cell 17 to which no electric field is beingapplied. Thus, transmission through or absorption and blocking by theupper polarizing plate 18, disposed on the light exit side of the lowerpolarizing plate 16, of the polarization component in the particulardirection, which has passed through the lower polarizing plate 16, canbe controlled by application or no application of an electric field toeach pixel area of the liquid crystal cell 17.

The backlight 14 includes a light source, and planarly emits light. Aknown surface light source device, constructed as the edge-light type(side-light type) or the direct-light type, can be used as the backlight14. The light source may be a known one composed of light emittingdiodes (LEDs), a cold-cathode tube, an incandescent lamp, an organic ELemitter, etc.

<<<Touch Panel Device 20>>>

The touch panel device 20 will now be described. The touch panel device20 comprises a laminate 20 a including touch panel sensors 30, and adetection control section 21 connected to the touch panel sensors 30.The laminate 20 a including the touch panel sensors 30 is disposed at aposition facing the display surface 12 a of the image display mechanism12. As described above, the touch panel device 20 is constructed as aprojection capacitive-coupled touch panel device, and plays a role as aninput device for inputting information.

In the embodiment illustrated in FIG. 2, the laminate 20 a of the touchpanel device 20 is composed of a cover layer 28, an adhesive layer 25, afirst touch panel sensor 31, an adhesive layer 24, a second touch panelsensor 32, and a low-refractive index layer 23, arranged in this orderfrom the viewer side, i.e. from the opposite side from the image displaymechanism 12. Thus, in the embodiment illustrated in FIG. 2, the touchpanel device 20 has two touch panel sensors 30.

The cover layer 28 is a light transmissive layer which functions as adielectric body, and may be comprised of, for example, a glass or resinfilm. The cover layer 28 functions as an input surface (tough surface,contact surface) to the touch panel device 20: information from outsidecan be inputted into the touch panel device 20 by bringing a conductor,e.g. a human finger 5, into contact with the cover layer 28. The coverlayer 28 forms the outermost viewer-side surface of the display device10 and functions, in the display device 10, as a cover to protect thetouch panel device 20 and the image display mechanism 12 from theoutside.

The cover layer 28 is bonded via the adhesive layer 25 to the firsttouch panel sensor 31. The first touch panel sensor 31 is bonded via theadhesive layer 24 to the second touch panel sensor 32. The adhesivelayer 24 and the adhesive layer 25 function as a dielectric body betweenelectrodes 40, provided in the first touch panel sensor 31 and thesecond touch panel sensor 32, and a conductor, e.g. a human finger 5, incontact with the cover layer 28. Various adhesive materials may be usedfor the adhesive layer 24 and the adhesive layer 25. The term “adhesive(layer)” as used herein includes the meaning of glue (layer).

The low-refractive index layer 23, provided on the image displaymechanism 12 side of the second touch panel sensor 32, is a layer whichis expected to function as an antireflection layer (AR layer). Thelow-refractive index layer 23 can prevent image-forming light from theimage display mechanism 12 from reflecting from the image displaymechanism 12-side surface of the touch panel device 20 and becomingstray light. The low-refractive index layer 23 may be replaced with anantireflection layer having a moth-eye structure comprising a largenumber of microprotrusions, or may be omitted. It is possible to bondthe laminate 20 a of the touch panel device 20 to the display surface 12a of the image display mechanism 12 e.g. via an adhesive layer. In thatcase, the low-refractive index layer 23 is not necessary.

Besides the layers illustrated, the laminate 20 a of the touch paneldevice 20 may comprise an additional functional layer(s) which isexpected to perform a particular function. It is possible to use afunctional layer that performs two or more functions. It is possible toimpart a function to a layer(s) (substrate(s) or adhesive layer(s)),e.g. the below-described substrates 35 of the touch panel sensors 30,contained in the laminate 20 a. Examples of functions which can beimparted to the laminate 20 a of the touch panel device 20 include ananti-glare (AG) function, an abrasion-resistant hard coat (HG) function,an antistatic (AS) function, an electromagnetic wave-shielding function,an antifouling function, etc.

The detection control section 21 of the touch panel device 20 isconnected to the touch panel sensors 30, and processes informationinputted via the cover layer 28. The detection control section 21includes a circuit (detection circuit) configured to be capable ofidentifying a contact position of a conductor (typically a human finger)5 on the cover layer 28 upon contact of the conductor 5 with the coverlayer 28. Further, the detection control section 21 is connected to thedisplay control section 13 of the image display mechanism 12, so thatprocessed input information can be transmitted to the display controlsection 13. The display control section 13 can prepare image informationbased on the input information and cause the image display mechanism 12to display an image corresponding to the input information.

The term “capacitive-coupled” and the term “projection”capacitive-coupled as used herein each have the same meaning as used inthe technical field of touch panels. The term “capacitive-coupled” isalso referred to as “capacitance”, “capacitance-coupled”, etc. in thetechnical field of touch panels; the term “capacitive-coupled” as usedherein has the same meaning as “capacitance”, “capacitance-coupled”,etc. A typical capacitance-coupled touch panel device includeselectrodes (conductive layer). Upon contact of an external conductor(typically a human finger) with a touch panel, a capacitance is formedbetween the external conductor and an electrode (conductive layer) ofthe touch panel device. Based on a change in the electrical state due tothe formation of the condenser, the positional coordinates of thecontact position of the external conductor on the touch panel can beidentified (detected).

<<Touch Panel Sensor 30>>

The touch panel sensor 30 will now be described in detail. As shown inFIGS. 2 and 3, the touch panel sensor 30 includes a sheet-like substrate35 and electrodes 40 formed on the substrate 35. In the embodimentillustrated in FIG. 2, the electrodes 40 are provided on the one-side(viewer-side) surface of the substrate 35.

The touch panel device 20 shown in FIG. 2 comprises the first touchpanel sensor 31 and the second touch panel sensor 32. The first touchpanel sensor 31 and the second touch panel sensor 32 can have the sameconstruction except that the electrodes 40 are arranged in differentpatterns. In the following description, those components which are equalbetween the first touch panel sensor 31 and the second touch panelsensor 32 will be described as components of the touch panel sensor 30without distinguishing between the first touch panel sensor 31 and thesecond touch panel sensor 32.

<Substrate 35>

The substrate 35 supports the electrodes 40, and functions as adielectric body in the touch panel sensor 30. As shown in FIGS. 1 and 3,the substrate 35 consists of an active area Aa1 corresponding to an areacapable of detecting a touch position, and a non-active area Aa2 lyingadjacent to the active area Aa1. As shown in FIG. 1, the active area Aa1of the touch panel sensor 30 occupies the area facing the display areaA1 of the image display mechanism 12. On the other hand, the non-activearea Aa2 is formed such that it entirely surrounds the periphery of therectangular active area Aa1, in other words, formed in a frame-likeshape. The non-active area Aa2 is formed in an area which faces thenon-display area A2 of the image display mechanism 12.

As will be described in more detail below, the electrodes 40 arecomposed of detection electrodes 50 for use in positional detection, andextraction electrodes 45 connected to the detection electrodes 50. Asshown in FIG. 3, the detection electrodes 50, which can form acapacitive coupling between it and an external conductor 5, are providedin the active area Aa1 of the substrate 35, while the extractionelectrodes 45 connected to the detection electrodes 50 are provided inthe non-active area Aa2 of the substrate 35.

The substrate 35 is transparent or translucent so that an image on theimage display mechanism 12 can be viewed through the active area Aa1.The light transmittance of the substrate 35 in the visible light rangeis preferably not less than 80%, more preferably not less than 84%. Thelight transmittance of the substrate 35 can be measured according to JISK7361-1 (test method for determining the total light transmittance oftransparent plastic material).

The substrate 35 may be formed of, for example, a glass or resin filmwhich can function as a dielectric body. Various resin films which arecommonly used for the substrates of optical members can be preferablyused as the resin film. For example, an optically isotropic film havingno birefringence, typically a film of a cellulose ester as typified bytriacetyl cellulose can be used as the substrate 35. On the other hand,an optically anisotropic film having birefringence can also be used asthe substrate 35. For example, a polyester film such as a polyethyleneterephthalate (PET) film, which is inexpensive and has excellentstability, can be used as the substrate 35. A polyester film has theadvantage that because of its low hygroscopic properties, deformationhardly occurs even in a hot and humid environment.

(Optical Anisotropy of the Substrate)

When the touch panel sensor 30 and the touch panel device 20 are used incombination with the image display mechanism 12 in which a particularpolarization component serves as image-forming light as in theillustrated embodiment, the use of an optically anisotropic film, astypified by a polyester film, as the substrate 35 can cause the problemof the occurrence of a visible multi-color pattern (hereinafter alsoreferred to as “rainbow pattern”). In this regard, it has been found inthe present inventors' studies that a rainbow pattern can be effectivelyobscured by using an optically anisotropic birefringent substrate 35having a total retardation of not less than 6000 nm. This will bedescribed in more detail below. Also for the cover layer 28 lying on theviewer side of the image display mechanism 12, the use of an opticallyanisotropic film as described herein is effective for preventing arainbow pattern.

From the viewpoint of preventing a rainbow pattern, the retardation ofthe substrate 35 is preferably not less than 6000 nm. On the other hand,there is no particular limitation on the upper limit of the retardationof the substrate 35; however, the upper limit is preferably about 30000nm. If the retardation of the substrate 35 exceeds 30000 nm, there willbe no further appreciable improvement in the prevention of a rainbowpattern and, in addition, the substrate 35 tends to be thick. Thus, fromthe viewpoints of prevention of a rainbow pattern and thinning of thesubstrate 35, the retardation of the substrate 35 is preferably 10000 to20000 nm.

The retardation (Re) as used herein is represented by the followingformula (1):Retardation (Re)=(n _(x) −n _(y))×d  (1)

where n_(x) represents the refractive index of the substrate 35 in thedirection (slow axis direction) in which the refractive index is maximumin the plane of the substrate 35, n_(y) represents the refractive indexin the direction (fast axis direction) perpendicular to the slow axisdirection, and d represents the thickness of the substrate 35.

The retardation value can be measured, for example, by using KOBRA-WR,manufactured by Oji Scientific Instruments, under the conditions ofmeasurement angle 0° and measurement wavelength 548.2 nm.

The value of (n_(x)−n_(y)) (hereinafter also expressed as Δn) in theabove formula (1) is preferably not less than 0.05. If the Δn value isless than 0.05, a sufficient rainbow pattern preventing effect may notbe achieved. Furthermore, an undesirably large thickness of thesubstrate 35 is required in order to obtain the above-describedretardation value. In more preferably, the lower limit of the Δn valueis 0.07.

A resin material for the optically anisotropic substrate 35 is notparticularly limited if it can satisfy the above-described retardationcondition. A preferable example of the resin material may be oneselected from the group consisting of a polyester resin, a polyolefinresin, a (meth)acrylic resin, a polyurethane resin, a polyether sulfoneresin, a polycarbonate resin, a polysulfone resin, a polyether resin, apolyether ketone resin, a (meth)acrylonitrile resin, and a cycloolefinresin.

A method for obtaining the optically anisotropic substrate 35 is notparticularly limited if it can satisfy the above-described retardationcondition. For example, when the substrate 35 is made of a polyesterfilm, a usable method comprises melting and extruding a polyester resininto a sheet, laterally stretching the unstretched polyester sheet usinge.g. a tenter at a temperature higher than the glass transitiontemperature, and then subjecting the stretched polyester sheet to heattreatment. The retardation of the transparent substrate produced by thismethod can be controlled at not less than 6000 nm by appropriatelysetting the stretch ratio, the stretch temperature, and the thickness ofthe transparent substrate. A higher retardation can be obtained bysetting a higher stretch ratio, a lower stretch temperature and a largersubstrate thickness. Conversely, a lower retardation can be obtained bysetting a lower stretch ratio, a higher stretch temperature and asmaller substrate thickness.

While the thickness of the substrate 35 may be appropriately determineddepending on the constituent material, etc., it is preferably in therange of 20 to 500 μm. If the thickness is less than 20 μm, theretardation of the substrate 35 sometimes cannot be made not less than6000 nm. Further, the mechanical properties of the substrate 35 may besignificantly anisotropic, and therefore the substrate 35 is likely totear or break. Thus, the usefulness of the substrate as an industrialmaterial can significantly decrease. On the other hand, if the thicknessexceeds 500 μm, the substrate will be very rigid and lack theflexibility peculiar to a polymer film. Thus, again, the usefulness ofthe substrate as an industrial material can significantly decrease. Thethickness of the substrate is more preferably not less than 30 μm andnot more than 400 μm, yet more preferably not more than 300 μm.

It has been found in the present inventors' studies that in combinationwith the image display mechanism 12 comprised of a liquid crystaldisplay device, the touch panel sensor 30 is preferably positioned withrespect to the liquid crystal display panel 15 such that the angleformed between the slow axis of the optically anisotropic substrate 35of the touch panel sensor 30 and the absorption axis of the upperpolarizing plate 18 of the image display mechanism 12 is in the range of0°±30° or 90°±30°, more preferably in the range of 0°±10° or 90°±10°,yet more preferably in the range of 0°±7° or 90°±7°, still morepreferably in the range of 0°±3° or 90°±3°, and most preferably 0° or90°. It has been found that the occurrence of a rainbow pattern can bevery effectively prevented by setting the angle formed between the slowaxis of the optically anisotropic substrate 35 of the touch panel sensor30 and the absorption axis of the upper polarizing plate 18 of the imagedisplay mechanism 12 in the above-described range.

<Electrodes 40>

The electrodes 40 of the touch panel sensor 30, provided on thesubstrate 35, will now be described.

As described above, the electrodes 40 are composed of detectionelectrodes 50 for use in positional detection, and extraction electrodes45 connected to the detection electrodes 50.

The electrodes 40 are formed of a material having electricalconductivity, and are electrically connected to the detection circuit ofthe detection control section 21 which is configured to detect a contactposition of an external conductor 5 on the cover layer 28. In theembodiment illustrated in FIG. 3, the electrodes 40 comprise a largenumber of detection electrodes 50 disposed in the active area Aa1 of thesubstrate 35, and a large number of extraction electrodes 45 connectedto the detection electrodes 50 and disposed in the non-active area Aa2of the substrate 35.

(The Overall Construction of Detection Electrodes 50)

The detection electrodes 50 of the first touch panel sensor 31 arearranged in a predetermined pattern on the one-side (viewer-side)surface of the substrate 35 of the first touch panel sensor 31. Thedetection electrodes 50 of the second touch panel sensor 32 arearranged, in a pattern different from that of the detection electrodes50 of the first touch panel sensor 31, on the one-side (viewer-side)surface of the substrate 35 of the second touch panel sensor 32. Morespecifically, as shown in FIG. 3, the detection electrodes 50 of thefirst touch panel sensor 31, when viewed macroscopically, areconstructed as linearly extending conductive wires (conductors) arrangedin one direction along the sheet plane of the first touch panel sensor31. On the other hand, the detection electrodes 50 of the second touchpanel sensor 32, when viewed macroscopically, are constructed aslinearly extending conductive wires (conductors) arranged in anotherdirection, intersecting the one direction, along the sheet plane of thesecond touch panel sensor 32. In the illustrated embodiment, the onedirection in which the detection electrodes 50 of the first touch panelsensor 31 are arranged is, on the panel plane of the touch panel sensor20, perpendicular to the another direction in which the detectionelectrodes 50 of the second touch panel sensor 32 are arranged.

As shown in FIG. 3, in the first touch panel sensor 31 and the secondtouch panel sensor 32, the conductive wires constituting the detectionelectrodes 50 of the electrodes 40 each extend linearly in a directionintersecting the direction (the one direction or the another direction)in which the conductive wires are arranged. Particularly in theillustrated embodiment, the detection electrodes 50 each extend in alinear direction perpendicular to the arrangement direction.

In the embodiment illustrated in FIG. 3, the detection electrodes 50 ofthe electrodes 40 each comprise a large number of spaced-apartconductive meshes 55 arranged with spaces in the longitudinal directionof the detection electrode 50, and connecting wires 51 each connectingtwo adjacent conductive meshes 55. Each detection electrode 50,consisting of the conductive meshes 55 and the connecting wires 51,extend linearly in the active area Aa1. As described below, in eachconductive mesh 55, thin conductive wires 60 are arranged in a meshpattern that defines a large number of open areas 71. As shown in FIG.3, the width of each detection electrode 50 is large in those portionswhere the conductive meshes 55 are disposed. The conductive meshes 55 ofeach detection electrode 50, shown in FIG. 3, each have an approximatelysquare contour in a plan view.

As shown in FIG. 3, when viewed in the normal direction to the panelplane of the touch panel device 20 (i.e. in a plan view), each detectionelectrode 50 contained in the first touch panel sensor 31 intersectswith the large number of detection electrodes 50 contained in the secondtouch panel sensor 32. As shown in FIG. 3, the conductive meshes 55 ofeach detection electrode 50 of the first touch panel sensor 31 are eachdisposed between two points of intersection between the detectionelectrode 50 and two adjacent detection electrodes 50 of the secondtouch panel sensor 32. Similarly, when viewed in the normal direction tothe panel plane of the touch panel device 20 (i.e. in a plan view), eachdetection electrode 50 contained in the second touch panel sensor 32intersects with the large number of detection electrodes 50 contained inthe first touch panel sensor 31. The conductive meshes 55 of eachdetection electrode 50 of the second touch panel sensor 32 are eachdisposed between two points of intersection between the detectionelectrode 50 and two adjacent detection electrodes 50 of the first touchpanel sensor 31. Further, in the illustrated embodiment, the conductivemeshes 55 of the detection electrodes 50 contained in the first touchpanel sensor 31 and the conductive meshes 55 of the detection electrodes50 contained in the second touch panel sensor 32, when viewed in thenormal direction to the panel plane of the touch panel device 20 (i.e.in a plan view), are disposed such that they do not overlap. Thus, whenviewed in the normal direction to the panel plane of the touch paneldevice 20 (i.e. in a plan view), the detection electrodes 50 containedin the first touch panel sensor 31 intersect with the detectionelectrodes 50 contained in the second touch panel sensor 32 only in theconnecting conductive wires 51 of the detection electrodes 50.

(Conductive Meshes 55)

The conductive meshes 55 form the thick portions of the detectionelectrodes 50, making it possible to detect with high sensitivity anexternal conductor 5 (e.g. a finger) in contact with a region, having acertain area, of the cover layer 28. On the other hand, the active areaAa1 in which the detection electrodes 50 are provided lies over thedisplay area A1 of the image display mechanism 12, and therefore needsto have a certain level of permeability to visible light. To ensurepermeability to visible light, in the areas of the conductive meshes 55,thin conductive wires 60 made of a metal material having a highelectrical conductivity are arranged in a mesh pattern.

As shown in FIG. 5, the thin conductive wires 60 of each conductive mesh55 have a large number of branch points 72. The thin conductive wires 60of each conductive mesh 55 are constructed as an assembly of a largenumber of boundary segments 73 which each form branch points 72 at bothends. That is, the thin conductive wires 60 of each conductive mesh 55are constructed as an assembly of a large number of boundary segments 73each extending between two branch points 73. The boundary segments 73,which are connected at the branch points 73, define open areas 71. Inother words, each open area 71 is surrounded and defined by a number ofboundary segments 73.

As shown in FIG. 5, in this embodiment the thin conductive wires 60consist only of the boundary segments 73: there is no thin conductivewires 60 extending into the open areas 71. This can effectively providethe touch panel sensor 30 with both a sufficient sensitivity forpositional detection and a high visible light transmittance.

(Mesh Pattern of Conductive Mesh 55)

Pixels for forming an image are regularly arranged in the display areaA1 of the image display mechanism 12, superimposed on the touch panelsensor 30. Because of the lamination of the image display mechanism 12having the pixel array and the touch panel sensor 30 having theconductive meshes 55, a stripe pattern, or moire, can appear due to theregular (periodic) pixel pattern and the arrangement pattern of the openareas 71 of each conductive mesh 55. In addition, a dark/light patterncan appear due to variation in the density of the open areas 71. Variousmethods are known to prevent the occurrence of moire and a dark/lightpattern; and such known methods may be appropriately applied to theconductive meshes 55.

On the other hand, it has been found in the present inventors' studiesthat moire can be very effectively prevented and, at the same time, adark/light pattern can be very effectively prevented by devising anarrangement pattern of the thin conductive wires 60 in each conductivemesh 55. The arrangement pattern of the thin conductive wires 60 in eachconductive mesh 55 in a plan view will now be described.

FIGS. 5 through 8 are diagrams illustrating an exemplary mesh pattern ineach conductive mesh 55. In the illustrated conductive mesh 55, in orderto prevent the occurrence of moire, there exists no linear direction inwhich open areas 71 are arranged at a pitch with repetition regularity(periodicity). It has been found in the present inventors' studies thatmoire which can be produced when the touch panel sensor 30 having theconductive meshes 55 is superimposed on the image display mechanism 12having the pixel array, or moire which can be produced when the twotouch panel sensors 30 each having the conductive meshes 55 aresuperimposed on each other, can be very effectively obscured not bymerely making the pattern of each conductive mesh 55 irregular, but bydesigning the pattern of each conductive mesh 55 in such a manner thatthere exists no linear direction in which open areas 71 are arranged ata constant pitch.

FIG. 6 is a plan view illustrating a mesh pattern in which there existsno direction in which open areas 71 are arranged at a constant pitch, inother words, open areas 71 are regularly arranged, or in other words,open areas 71 are lined up with regularity. In FIG. 6, a hypotheticalline d_(i), extending in an arbitrary position and in an arbitrarydirection, is selected on the sheet plane of the touch panel sensor 30.The line d_(i) intersects with boundary segments 73 and forms points ofintersection. The points of intersection are indicated as cross-pointsC₁, C₂, C₃, . . . C₉, numbered from the lower-left one in FIG. 6. Thedistance between two adjacent cross-points, e.g. cross-point C₁ andcross-point C₂, is the size T₁ of an open area 71 on the line d_(i). Foranother open area 71 lying adjacent to the open area 71 of the size T₁along the line d_(i), the size T₂ of the open area 71 on the line d_(i)can be determined in the same manner. In this manner, for the line d_(i)extending in an arbitrary position and in an arbitrary direction, thesizes T_(i), T₂, T₃, . . . T₈ of those open areas 71 which the lined_(i) pass across can be determined. There is no periodicity(regularity) in the line of the numerical values T₁, T₂, T₃, . . . T₈.Thus, the open areas 71 are arranged along the linear direction d₁ withno regularity and, in addition, the following condition is met:T _(k) ≠T _(k+l)(k: arbitrary natural number, l: arbitrary naturalnumber)   (x)

For easier understanding, the T₁, T₂, T₃, . . . T₈, together with theline d_(i), are depicted at the bottom of FIG. 6 separately from theconductive mesh 55.

When the sizes T₁, T₂, . . . of open areas 71 are determined for ahypothetical line d_(i+1) extending in a direction determined byrotating the line d_(i) shown in FIG. 6 through an arbitrary angle, thecondition (x) is met also for the line d_(i+1), and there is norepetition periodicity (regularity) in the sizes T₁, T₂, . . . . In thecase where open areas 71 meet the condition (x) in any direction, themesh pattern is herein expressed as “there exists no direction in whichopen areas 71 are arranged at a constant pitch” or “there exists nodirection in which open areas 71 are regularly arranged” or “thereexists no direction in which open areas 71 are arranged with repetitionperiodicity” or “open areas 71 are arranged with no regularity”.

To make the pattern of each conductive mesh irregular is generallyconsidered to be effective for preventing the occurrence of moire.However, it has been found in the present inventors' studies that moirecannot be always sufficiently obscured by merely making irregular theshape and the arrangement pitch of the pattern of each conductive mesh.It has also been found that even if moire can be obscured, a dark/lightpattern can sometimes occur in the conductive meshes.

On the other hand, it has been found that the occurrence of moire can beeffectively prevented and the occurrence of a dark/light pattern canalso be effectively prevented if, as with the pattern of each conductivemesh 55 according to this embodiment, the pattern of each conductivemesh 55 is designed in such a manner that there exists no lineardirection in which open areas (closed circuits) 71 are arranged at aconstant pitch and, in addition, if a restriction is imposed on theaverage of the number of boundary segments 73 extending from each branchpoint 72 as will be described below. Such technical effects areconsidered to be remarkable and unexpected ones in view of the technicallevel of the prior art in which merely making the mesh pattern irregularhas been practiced in order to prevent moire.

In the conductive meshes 55 shown in FIGS. 5 and 7, the average of thenumber of boundary segments 73 extending from each branch point 72 isnot less than 3.0 and less than 4.0. By making the average of the numberof boundary segments 73 extending from each branch point 72 not lessthan 3.0 and less than 4.0, the arrangement pattern of each conductivemesh 55 can be made significantly different from a square latticepattern. By making the average of the number of boundary segments 73extending from each branch point 72 more than 3.0 and less than 4.0,each conductive mesh 55 can be made to have a honeycomb arrangementpattern with reduced regularity. Further, it has been found in thepresent inventors' studies that by making the average of the number ofboundary segments 73 extending from each branch point 72 not less than3.0 and less than 4.0, the arrangement of the open areas 71 can be madeirregular so that there stably exists no direction in which open areas71 are arranged with repetition regularity (periodicity), thereby makingit possible to very effectively obscure moire.

Furthermore, the occurrence of a noticeable dark/light pattern can beprevented by imposing the above-described restriction on the average ofthe number of boundary segments 73 extending from each branch point 72.Though the reason why a dark/light pattern can be prevented has not yetbeen fully elucidated, it may be due to the fact that the in-planedispersion of the open areas 71 becomes uniform to some extent byimposing the above-described restriction on the average of the number ofboundary segments 73 extending from each branch point 72.

The average of the number of boundary segments 73 extending from eachbranch point 72 should strictly be determined by determining the numberof boundary segments 73 extending from all the branch points 72contained in the conductive mesh 55, and then calculating the averagevalue. In practice, however, it is possible to use a method comprising:selecting a region having an area which is expected to be capable ofreflecting the overall trend of the number of boundary segments 73extending from each branch point 72, taking into consideration the sizeof each open area 71 defined by thin conductive wires 60, etc.;determining the number of boundary segments 73 extending from all thebranch points 72 contained in the region; and calculating the averagevalue. The calculated value is treated as the average of the number ofboundary segments 73 extending from each branch point 72, determined forthe entire conductive mesh 55. For example, in the conductive meshes 55formed in the active area Aa1 of the touch panel sensor 30, each openarea 71 has an opening area which is equal to the area of a circlehaving a diameter of 100 μm to 600 μm. In the case of the conductivemeshes 55 of the touch panel sensor 30 having the open areas 71 of suchdimensions, a 30 mm×30 mm region may be selected in a conductive mesh55, and the average of the number of boundary segments 73 extending fromeach branch point 72, calculated for the branch points 72 contained inthe region, may be treated as the average value determined for theentire conductive mesh 55.

Likewise, whether there exists a direction in which open areas 71 arearranged at a constant pitch should strictly be determined for all theopen areas 71 that exist in any direction in the entire area of a targetconductive mesh 55. In practice, however, it is possible to use thefollowing method: A region having an area which is expected to becapable of reflecting the overall trend of the arrangement of the openareas 71 (e.g. a 30 mm×30 mm region in the case of a conductive mesh 55in which the open areas 71 having the above-described dimensions areformed) is selected. In the selected region, the arrangement of openareas 71 is checked in those directions which pass through a centralpoint in the region and which are equally spaced apart at an angle whichis expected to be capable of reflecting the trend of periodicity in alldirections (e.g. at an angle of 15° in the case of a conductive mesh 55in which the open areas 71 having the above-described dimensions areformed) to determine whether there exists a direction in which openareas 71 are regularly arranged.

In the conductive mesh 55 of the touch panel sensor 30, shown in FIG. 5,the average of the number of boundary segments 73 extending from eachbranch point 72 is more than 3.0 and less than 4.0. More specifically,of 387 target branch points 72, 3 boundary segments 73 extend from eachof 373 branch points 72, and 4 boundary segments 73 extend from each ofthe other 14 branch points 72. Thus, the average number of boundarysegments (average number of branches) extending from each branch point72 is 3.04. When the conductive mesh 55 shown in FIG. 5 was actuallyproduced and disposed on the pixel array of a commercially-availableliquid crystal display device, a visible stripe pattern moire(interference pattern) and a visible dark/light pattern were notobserved.

Further, the present inventors' studies of various patterns of theconductive mesh 55 have revealed that a visible dark/light pattern andmoire both can be more obscured if at least one of the followingconditions (A), (B) and (C) is met:

Condition (A): Those open areas 71 which are surrounded by 6 boundarysegments 73 are contained most in the conductive mesh 55. That is, thoseopen areas 71 which are surrounded by 6 boundary segments 73 arecontained in a larger number in the conductive mesh 55 as compared tothose open areas 71 which are surrounded by any other number of boundarysegments 73.

Condition (B): The following condition (b1) is met. Preferably, thefollowing condition (b1) and one of the following conditions (b2) and(b3) are met. More preferably, all of the following conditions (b1),(b2) and (b3) are met:

(b1) At least two of an open area(s) 71 surrounded by 5 boundarysegments 73, an open area(s) 71 surrounded by 6 boundary segments 73 andan open area(s) 71 surrounded by 7 boundary segments 73 are eachcontained plurally in the conductive mesh 55.

(b2) A plurality of those open areas 71 which are surrounded by 5, 6 or7 boundary segments 73 are not equal in at least one of the area and theshape. Thus, in the case where a plurality of those open areas 71 whichare surrounded by 5 boundary segments 73 are contained in the conductivemesh 55, at least two of the open areas 71 defined by 5 boundarysegments 73 differ from each other in at least one of the area and theshape. In the case where a plurality of those open areas 71 which aresurrounded by 6 boundary segments 73 are contained in the conductivemesh 55, at least two of the open areas 71 defined by 6 boundarysegments 73 differ from each other in at least one of the area and theshape. In the case where a plurality of those open areas 71 which aresurrounded by 7 boundary segments 73 are contained in the conductivemesh 55, at least two of the open areas 71 defined by 7 boundarysegments 73 differ from each other in at least one of the area and theshape.

(b3) A plurality of those open areas 71 which are surrounded by 6boundary segments 73 are contained in the conductive mesh 55.

Condition (C): The number N_(k) of those open areas 71 which aresurrounded by k boundary segments 73 satisfy the following relations:N_(k)≦N_(k+1) when k is an integer that satisfies 3≦k≦5; andN_(k)≧N_(k+1) when k is an integer that satisfies 6≦k

Thus, those open areas 71 which are surrounded by 6 boundary segments 73are contained most in the conductive mesh 55. The number of open areas71 decreases as the number of boundary segments 73 that surround each ofthe open areas 71 increases from 6, and also as the number of boundarysegments 73 that surround each of the open areas 71 decreases from 6.

In a strict sense, whether the conditions (A) to (C) are met or notshould be determined for all the open areas 71 contained in theconductive mesh 55. In practice, however, it is possible to use thefollowing method: A region having an area which is expected to becapable of reflecting the overall trend of the number of boundarysegments 73 surrounding each open area 71 (e.g. a 30 mm×30 mm region inthe case of a conductive mesh 55 in which the open areas 71 having theabove-described dimensions are formed) is selected taking intoconsideration the size of each open area 71 defined by thin conductivewires 60, etc. In the selected region, the number of boundary segments73 surrounding each open area 71 is determined to determine whether theconditions (A) to (C) are met.

The technical effects achieved by the conductive meshes 55 which meet atleast one of the conditions (A) to (C) are considered to be remarkableand unexpected ones in view of the technical level of the prior art inwhich merely making the mesh pattern irregular has been practiced inorder to prevent moire. Though the reason why such technical effects areachieved by the conductive meshes 55 which meet at least one of theconditions (A) to (C) has not yet been fully elucidated, the followingcan be considered a cause. However, the present invention is not boundby the theory.

When each conductive mesh 55 meets at least one of the conditions (A) to(C), the arrangement of the open areas 71 can be one which correspondsto a honeycomb arrangement comprising regularly-arranged regularhexagons having the same shape, but in which regularity of the shape andthe arrangement of the open areas is reduced, in other words, ahoneycomb arrangement which is randomized in the shape and thearrangement of the open areas. It is considered that this can prevent anappreciable variation in the density of the open areas 71, making itpossible to distribute a large number of open areas 71 approximately ata uniform density, i.e. approximately uniformly. Accordingly, thearrangement of the open areas 71 can be stably made completelyirregular, i.e. the arrangement of the open areas 71 can be stably madeirregular such that there exists no direction in which open areas 71 areregularly arranged. Therefore, compared to the case of merely making thearrangement of the open areas irregular, both a visible dark/lightpattern and moire can be effectively obscured.

The applicants conducted an experiment to examine a conductive mesh 55having the pattern shown in FIG. 7. As a result, as shown in FIG. 8, theconductive mesh 55 was found to contain 79, 1141, 2382, 927, 94 and 8open areas 71 which are each surrounded by 4, 5, 6, 7, 8 and 9 boundarysegments 73, respectively. It was also found that the conductive mesh 55contains no open areas 71 which are each surrounded by 3 boundarysegments 73 and no open areas 71 which are each surrounded by 10 or moreboundary segments 73. Thus, the conductive mesh 55 shown in FIG. 7 meetsall the conditions (A), (B) and (C). Furthermore, it was found that inthe conductive mesh 55 shown in FIG. 7, there exists no direction inwhich open areas 71 are arranged at a constant pitch and, in addition,the average of the number of boundary segments 73 extending from eachbranch point 72 is not less than 3.0 and less than 4.0. When theboundary segments 73 are straight line segments, an open area 71surrounded by N boundary segments 73 has an N-sided polygonal shape.When the conductive mesh 55 shown in FIG. 7 was actually produced anddisposed on the pixel array of the image display mechanism 12, a visiblestripe pattern moire (interference pattern) and a visible dark/lightpattern were not observed.

The following is a description of an exemplary method for producing aconductive mesh pattern in which the average of the number of boundarysegments 73 extending from each branch point 72 is more than 3.0 andless than 4.0 and, in addition, there exists no direction in which openareas 71 are arranged at a constant pitch.

The method comprises the steps of: determining base points; preparing aVoronoi diagram from the determined base points; determining a pathwayfor a boundary segment extending between two Voronoi points connected bya Voronoi boundary in the Voronoi diagram; and determining the thicknessof the determined pathway to define the boundary segment, therebydetermining a mesh pattern of a conductive mesh 55 (thin conductivewires 60). The respective steps will now be described in order. Theabove-described mesh pattern of the conductive mesh 55 shown in FIG. 5was actually determined by the below-described method. The mesh patternof the conductive mesh 55 shown in FIG. 7 can also be determined by thebelow-described method.

The step of determining base points will be described first. At theoutset, as shown in FIG. 9, a first base point BP1 is plotted at anarbitrary position on an absolute coordinate system O-X-Y. Next, asshown in FIG. 10, a second base point BP2 is plotted at an arbitraryposition at a distance r from the first base point BP1. In other words,a second base point BP2 is plotted at an arbitrary position on a circlewith a radius r (hereinafter referred to as “first circle”), centered atthe first base point BP1 and lying on the absolute coordinate systemO-X-Y. Next, as shown in FIG. 11, a third base point BP3 is plotted atan arbitrary position at a distance r from the first base point BP1 andat a distance of not less than r from the second base point BP2.Thereafter, a fourth base point BP4 is plotted at an arbitrary positionat a distance r from the first base point BP1 and at a distance of notless than r from the other base points BP2, BP3.

In this manner, base points are plotted at an arbitrary position at adistance r from the first base point BP1 and at a distance of not lessthan r from the other base points until the next base point cannot beplotted any more. Thereafter, the same operation is performed withreference to the second base point BP2. Thus, the next point is plottedat an arbitrary position at a distance r from the second base point BP2and at a distance of not less than r from the other base points. In thismanner, base points are plotted at an arbitrary position at a distance rfrom the second base point BP2 and at a distance of not less than r fromthe other base points until the next base point cannot be plotted anymore. Thereafter, base points are produced successively by the sameprocedure while changing reference base points in order.

Base points are plotted successively by the above procedure until a basepoint cannot be plotted any more in an area in which a conductive mesh55 is to be formed. The step of producing base points is completed whena base point cannot be plotted any more in the area in which theconductive mesh 55 is to be formed. When the above process is complete,base points which are irregularly plotted on the two-dimensional plane(XY plane) are uniformly dispersed in the area in which the conductivemesh 55 is to be formed.

With regard to the base points BP1, BP2, BP6 (see FIG. 12(A)) thusproduced and distributed in the two-dimensional plane (XY plane), thedistances between adjacent base points are not constant but have adistribution. The distribution of the distances between any two adjacentbase points is not a completely random distribution (uniformdistribution): the distances are distributed in the range ΔR between theupper limit R_(MAX) and the lower limit R_(MIN) (ΔR=R_(MAX)−R_(MIN)),with the average R_(AVE) lying in the range. The “two adjacent basepoints” are herein defined as follows: if, after preparing thebelow-described Voronoi diagram from the base points BP1, BP2, . . . ,two Voronoi regions XA lie adjacent to each other, then the base pointsof the two Voronoi regions XA are defined as two adjacent base points.

In particular, on a coordinate system in which each of the above basepoints is taken as the origin (such a coordinate system is referred toas a relative coordinate system o-x-y, while a coordinate system thatdefines the real two-dimensional plane is referred to as an absolutecoordinate system O-X-Y), all the base points lying adjacent to the basepoint as the origin are plotted to obtain a graph such as one shown inFIG. 12(B). Such graphs of FIG. 12(B), FIG. 12(C), . . . are obtained byusing all the above base points as the origin. All the thus-obtainedgraphs of adjacent base points on the respective relative coordinatesystems are then overlapped to obtain a graph as shown in FIG. 12(D).The distribution pattern of adjacent base points on the relativecoordinate system, shown in the resulting graph, indicates that thedistances between any two adjacent base points are not uniformlydistributed in the range from 0 to infinity, but distributed in thefinite range from R_(AVE)−ΔR to R_(AVE)+ΔR (in the toroidal area withthe radius ranging from R_(MIN) to R_(MAX)). In FIG. 12(A), Voronoiboundaries (see FIG. 13) obtained from the base points are shown bybroken lines for reference.

By setting the distances between base points in the above-describedmanner, the dimensions of Voronoi regions XA obtained from the basepoints by the below-described method, and also the dimensions of openareas 71 obtained from the Voronoi regions can be made to be distributednot uniformly (completely randomly) but in a finite range.

A size of open area 71 can be adjusted by changing the distance r in theabove-described step of determining base points. In particular, a sizeof open area 71 can be decreased by decreasing the distance r.Conversely, a size of open area 71 can be increased by increasing thedistance r.

Next, as shown in FIG. 13, a Voronoi diagram is prepared based on theplotted base points. As shown in FIG. 13, a Voronoi diagram is composedof line segments connected at points of intersection betweenperpendicular bisectors which are each drawn between two adjacent basepoints. The line segments of the perpendicular bisectors are hereinreferred to as Voronoi boundaries XB; the points of intersection betweenVoronoi boundaries XB, which form the end points of Voronoi boundariesXB, are herein referred to as Voronoi points XP; and the regionssurrounded by Voronoi boundaries XB are herein referred to as Voronoiregions XA.

In the Voronoi diagram shown in FIG. 13, the Voronoi points XP are usedas the branch points 72 of the conductive mesh 55. One boundary segment73 is provided between two Voronoi points XP that form the end points ofone Voronoi boundary XB. As in the embodiment illustrated in FIG. 5,such a boundary segment 73 may be designed as a straight line extendinglinearly between two Voronoi points XP. Alternatively, such a boundarysegment 73 may be designed to extend between two Voronoi points XP in avariety of pathways (for example, a curved line such as a circular arc,an elliptical arc, a parabola, a hyperbola, a sine curve, a hyperbolicsine curve, an elliptic function curve or a Bessel function curve, apolygonal line, etc.) without contact with other boundary segment 73.When the boundary segments 73 are designed to each extend linearlybetween two Voronoi points XP, the boundary segments 73 coincide withthe Voronoi boundaries XB.

After determining the pathways of the boundary segments 73, the linewidth (thickness) of the boundary segments 73 is determined. For thereasons described below, the line width of the boundary segments 73 ispreferably made 0.2 μm to 2 μm so that the conductive mesh 55 can havethe desired visible light transmittance and surface resistivity. Thepattern of the conductive mesh 55 can be determined in the mannerdescribed hereinabove.

(Extraction Electrodes 45)

The extraction electrodes 45 will now be described. As described above,the electrodes 40 include the extraction electrodes 45 connected to theabove-described detection electrodes 50. Depending on the methodemployed to detect a contact position, one or two extraction electrodes45 are provided for each detection electrode 50. Each extractionelectrode 45 comprises an extraction wire 46 connected to the connectingwire 51 of the corresponding detection electrode 50 or to the thinconductive wires 60 of the conductive mesh 55 of the correspondingdetection electrode 50. Each extraction electrode 45, in at least a partthereof in the thickness direction, is formed of the same material asand formed integrally with the corresponding detection electrode 50, aswill be described below. Each extraction electrode 45 extends, in thenon-active area Aa2 of the substrate 35, from the correspondingdetection electrode 50 to the peripheral edge of the substrate 35. Eachextraction electrode 45, at its end, is connected to the detectioncontrol section 21 via a not-shown external connecting wire (e.g. FPC).

(Cross-Sectional Shape of Electrode 40)

The cross-sectional shape of each electrode 40 will now be described.FIG. 4 shows the touch panel sensor 30 in a cross-section along thethickness direction. The “cross-section along the thickness direction”herein refers to a cross-section along the normal direction to the sheetplane (film plane, plate plane, panel plane) of the sheet-shaped(film-shaped, plate-shaped, panel-shaped) touch panel sensor 30. Theterm “sheet plane (film plane, plate plane, panel plane)” herein refersto a plane which coincides with the planar direction of an objectivesheet-shaped (film-shaped, plate-shaped, panel-shaped) member whentaking a wide and global view of the member. In this embodiment thesubstrate 35 has a sheet-like shape with the pair of main surfaces.Thus, in this embodiment, the “cross-section along the thicknessdirection” coincides with a cross-section along the normal direction tothe surfaces of the substrate 35.

FIG. 4 shows the cross-sectional shape of each thin conductive wire 60of a conductive mesh 55. Each connecting wire 51 of the detectionelectrode 50 has the same cross-sectional shape as each thin conductivewire 60 except that they differ only in the width. Thus, as shown inFIG. 4, the thin conductive wires 60 and the connecting wires 51,constituting the detection electrode 50, each have a base surface 66 onthe substrate 35 side, a flat top surface 67 located opposite to thebase surface 66, and a pair of side surfaces 68 extending between thebase surface 66 and the top surface 67. In the embodiment illustrated inFIG. 4, the base surface 66 and the top surface 67 are parallel to eachother. Further, in the embodiment illustrated in FIG. 4, each thinconductive wire 60 and each connecting wire 51 comprise a metal layer 61located on the substrate 35 side and having the base surface 66, and ablackened layer 62 provided on the metal layer 61 and having the topsurface 67. The metal layer 61 is formed integrally between theconnecting wire 51 and the thin conductive wires 60 of the conductivemeshes 55, and the blackened layer 62 is formed integrally between theconnecting wire 51 and the thin conductive wires 60 of the conductivemeshes 55.

The metal layer 61 is formed of a metal material having a highelectrical conductivity, such as copper, aluminum, iron, silver, or analloy thereof. The metal layer 61 has a relatively high reflectance.When external light is reflected from the metal layer 61 constitutingthe detection electrodes 50 of the touch panel sensor 30, the contrastof an image on the image display mechanism 12 as viewed through theactive area Aa1 of the touch panel device 20 becomes lower. In view ofthis, the blackened layer 62 is disposed on the viewer side of the metallayer 61. The blackened layer 62 can enhance image contrast, therebyimproving the visibility of images displayed by the image displaymechanism 12.

Any of a variety of known layers can be used as the blackened layer 62.The blackened layer 62, composed of a metal oxide or a metal sulfide,may be formed in a part of the metal layer 61 by subjecting the part toblackening treatment. Alternatively, the blackened layer 62, such as acoating film of a black material or a plating layer of nickel, chromium,or the like, may be formed on the metal layer 61. For example, when themetal layer 61 is made of iron, the metal layer 61 may be exposed to asteam atmosphere at about 450 to 470° C. for 10 to 20 minutes to form anoxide film (blackened film) having a thickness of about 1 to 2 μm in thesurface of the metal layer 61. Alternatively, the metal layer 61 made ofiron may be treated with a chemical, such as concentrated nitric acid,to form an oxide film (blackened film) in the surface of the metal layer61. When the metal layer 61 is made of copper, the metal layer 61 ispreferably subjected to cathodic electrodeposition in an electrolyticsolution, e.g. comprising sulfuric acid, copper sulfate and cobaltsulfate, to deposit cationic particles onto the metal layer 61. Thedeposition of cationic particles can roughen the metal layer 61 and, atthe same time, can achieve blackening of the layer. The cationicparticles may be copper particles or particles of an alloy of copper andother metal(s), preferably particles of a copper-cobalt alloy. From theviewpoint of black density, the cationic particles preferably have anaverage particle size of about 0.1 to 1 μm. The blackened layer 62herein includes not only a blackened layer but also a roughened layer.

The extraction wire 46 of each extraction electrode 45 may have the samecross-sectional shape as that of the thin conductive wire 60 or theconnecting wire 51 of each detection electrode 50, shown in FIG. 4.Thus, the extraction wire 46 of each extraction electrode 45 has a basesurface 66 on the substrate 35 side, a flat top surface 67 locatedopposite to the base surface 66, and a pair of side surfaces 68extending between the base surface 66 and the top surface 67. The basesurface 66 and the top surface 67 of the extraction wire 46 may beparallel to each other as shown in FIG. 4. The extraction wire 46 ofeach extraction electrode 45 includes a metal layer 61 in across-section in the thickness direction. The metal layer 61 of eachextraction electrode 45 is formed integrally with the metal layer 61 ofthe corresponding detection electrode 50. Thus, the electrode 40, in anycross-section thereof in the thickness direction, includes the metallayer 61 which occupies at least part of the cross-section.

On the other hand, the extraction electrodes 45 are disposed in thenon-active area Aa2 that faces the non-display area A2 of the imagedisplay mechanism 12. Therefore, the extraction wires 46 of theextraction electrodes 45 need not have the blackened layer 62. However,in order to avoid cumbersome patterning of the blackened layer 62, theextraction wires 46 of the extraction electrodes 45 may have theblackened layer 62 as with the detection electrodes 50. In that case,the blackened layer 62 of each extraction electrode 45 may be formedintegrally with the blackened layer 62 of the corresponding detectionelectrode 50.

In the illustrated embodiment the electrodes 40 each consist of themetal layer 61 and the blackened layer 62; however, instead of or inaddition to the blackened layer 62, some other layer(s) may be laminatedto the metal layer 61. The some other layer is, for example, ananti-rust layer.

In the electrodes 40 having the above construction, the width (maximumwidth) W of each thin conductive wire 60 constituting a conductive mesh55, shown in FIG. 4, i.e. the width (maximum width) W along the sheetplane of the sheet-shaped touch panel sensor 30, is preferably made notless than 1 μm and not more than 5 μm, and the height (thickness) H ofeach thin conductive wire 60 constituting a conductive mesh 55, shown inFIG. 4, i.e. the height (thickness) H in the normal direction to thesheet plane of the sheet-shaped touch panel sensor 30, is preferablymade not less than 0.2 μm and not more than 2 μm. The conductive meshes55 having such dimensions, because of the thin conductive wires 60 whichare made sufficiently thinned, can very effectively make the electrodes40 invisible. Furthermore, because of the sufficient height of the topsurface 67 from the base surface 66, which surfaces are parallel to eachother in the cross-sectional shape of each thin conductive wire 60, i.e.because of the sufficiently high aspect ratio (H/W) of thecross-sectional shape of each thin conductive wire 60, the thinconductive wires 60 can have a high electrical conductivity. The surfaceresistivity of the conductive meshes 55 can therefore be made not morethan 50Ω/□, preferably not more than 20Ω/□.

Thus, according to the thin conductive wires 60 having suchcross-sectional dimensions, the thin conductive wires 60, constitutingthe electrodes 40 of the touch panel sensor 30, can be thinned whilemaintaining the electrodes 40 at a low resistance. The thinned thinconductive wires 60, even in combination with high-definition pixels orwith short-pitch pixels provided in a portable terminal, called atablet, can achieve a high detection accuracy while sufficiently makingthe detection electrodes 50 invisible.

From the viewpoint of making the electrodes 40 invisible, the width Walong the sheet plane of the sheet-shaped touch panel sensor 30 ispreferably not more than 5.0 μm, more preferably not more than 3.5 μmand, from the viewpoint of reducing the surface resistivity, ispreferably not less than 1 μm, more preferably not less than 2 μm. Fromthe viewpoint of stabilizing the accuracy of the production of theelectrodes 40, the height (thickness) H in the normal direction to thesheet plane of the sheet-shaped touch panel sensor 30 is preferably notmore than 2.0 μm, more preferably not more than 1.5 μm and, from theviewpoint of reducing the surface resistivity, is preferably not lessthan 0.1 μm, more preferably not less than 0.5 μm. In addition, from theviewpoint of ensuring the technical effects described above, the aspectratio (H/W) of the cross-sectional shape of each thin conductive wire 60is preferably not less than 0.04 and not more than 2.00, more preferablynot less than 0.67 and not more than 7.00.

The cross-sectional shape of each thin conductive wire 60, shown in FIG.4, is tapered: the width W₂ at the top surface 67 is narrower than thewidth W₁ at the base surface 66. Particularly in the illustrateembodiment, the width of each thin conductive wire 60 changes such thatit solely decreases in a direction from the base surface 66 toward thetop surface 67, in other words, in a direction toward the viewer. Inparticular, in the illustrate embodiment, the width of each thinconductive wire 60 continuously decreases in a direction from the basesurface 66 toward the top surface 67, in other words, in a directiontoward the viewer. When the touch panel sensor 30 is incorporated intothe display device 10 and the touch panel device 20 such that the topsurface 67 faces the viewer as shown in FIG. 2, the contrast of an imagedisplayed by the image display mechanism 12 can sometimes become low dueto reflection of external light from the metal layer 61 exposed on theside surfaces 68. In view of this, the difference between the width W₁at the base surface 66 and the width W₂ at the top surface 67 (W₁−W₂) ispreferably not more than 1.0 μm, more preferably not more than 0.5 μm.

When the thin conductive wires 60 are produced by patterning using aphotolithography technique as will be described below, erosion byetching progresses not only in the depth direction (thickness direction)but in the lateral direction (planar direction) as well. The thinconductive wires 60 can be made to have a tapered cross-sectional shapeas shown in FIG. 4 by utilizing the side etching phenomenon.

On the other hand, according to the below-described method for theproduction of the touch panel sensor 30, the height of the connectingwires 51 of the detection electrodes 50 and the height of the extractionwires 46 of the extraction electrodes 45 are equal to the height of thethin conductive wires 60 constituting the conductive meshes 55 of thedetection electrodes 50. In that case, the width of each of theconnecting wires 51 of the detection electrodes 50 can be made not lessthan 5.0 μm, and the width of each of the extraction wires 46 of theextraction electrodes 45 can be made not less than 5.0 μm.

(Method for Producing Touch Panel Sensor 30)

An exemplary method for producing the above-described touch panel sensor30 will now be described mainly with reference to FIG. 14.

First, a substrate 35 is prepared as shown in FIG. 14(a). As describedabove, a glass or resin film can be used as the substrate 35. When aresin film having optical anisotropy is used as the substrate 35, theretardation Re of the resin film is preferably adjusted to theabove-described value in order to obscure a rainbow pattern.

Next, as shown in FIG. 14(b), a metal film 81, which is to make themetal layer 61 of each electrode 40, is formed on the substrate 35. Themetal film 81 is not formed by laminating a metal foil, such as a copperfoil, onto the substrate 35 via an adhesive layer, but formed directlyon the substrate 35 without an adhesive layer. Thus, the metal film 81is formed not by laminating an available metal foil having a certainthickness onto the substrate 35, but by depositing a film to a certainthickness on the substrate 35. Any of various film-forming(film-depositing) methods, such as sputtering, vapor deposition,electroplating, electroless plating, etc. can be used to form the metalfilm 81.

Vapor deposition is preferably employed to form the metal film 81 with athickness of 0.2 to 2 μm in order to adjust the height (thickness) H ofeach electrode 40 to 0.2 to 2 μm as described above. The use of a vapordeposition method can produce the metal film 81 having a thickness of0.2 to 2 μm, in particular not less than 0.5 μm, at a low cost in arelatively short time. The metal film 81 can also be effectively formedby a multi-step process comprising a sputtering step and a later step(s)performed by other method(s) such as electroplating. A base layer havingexcellent adhesive properties can be formed by the sputtering step. Thethickness of the metal layer 81 can be relatively quickly increased to adesired thickness by the later electroplating step.

Thereafter, as shown in FIG. 14(c), a blackened film 82, which is tomake the blackened layer 62 of each electrode 40, is formed on the metalfilm 81. As described previously, a surface portion of the metal film 81may be subjected to blackening treatment to form the blackened film 82,composed of a metal oxide or a metal sulfide, in the surface portion ofthe metal film 81. It is also possible to provide the blackened film 82,such as a coating film of a black material or a plating layer of nickel,chromium, or the like, on the metal film 81.

Next, the metal film 81 and the blackened film 82 on the substrate 35are subjected to patterning using a photolithography technique. Morespecifically, a resist film 83 is provided on the blackened film 82, andthe resist film 83 is patterned by pattern exposure and development(FIG. 14(d)). Next, using the patterned resist film 83 as a mask, theblackened film 82 and the metal film 81 are etched to form a blackenedlayer 62 and a metal layer 61 from the blackened film 82 and the metalfilm 81, respectively. In this manner, electrodes 40 comprising themetal layer 61 and the blackened layer 62 are formed in a desiredpattern on the substrate 35 (FIG. 14(e)).

Thereafter, the resist film 83 on the electrodes 40 is removed to obtaina touch panel sensor 30. The above production method can produce thedetection electrodes 50, each consisting of the metal layer 61 and theblackened layer 62, and the extraction electrodes 45, each consisting ofthe metal layer 61 and the blackened layer 62, integrally by the sameprocess, which is desirable in the light of production efficiency.

Further, according to the above production method, the total thicknessof the metal film 81 and the blackened film 82 which are to be etched,can be made equal to the thickness of the electrodes 40 produced, e.g.not less than 0.2 μm and not more than 2 μm. By etching the metal film81 and the blackened film 82 having such a total thickness, thinelectrodes 40 having a line width of about 1 μm to 5 μm can be producedwithout causing significant side etching. Thus, the total thickness ofthe metal film 81 and the blackened film 82 is not too large for theline width of thin conductive wires 60 to be formed. Therefore, unlikethe case of using a metal foil, described above with reference to FIG.21, it is not likely that adjacent eroded portions connect with eachother below the resist film 83. The thinned electrodes 40 (thinconductive wires 60) can therefore be produced stably with highaccuracy. In addition, by setting the total thickness of the metal film81 and the blackened film 82 at a value appropriate for the line widthof thin conductive wires 60 to be formed, it becomes possible for theresulting thin conductive wires 60 to have a desired cross-sectionalshape, e.g. a shape having a desired aspect ratio, in the thicknessdirection.

The above-described method for the production of the touch panel sensor30 is merely an example, and is capable of various changes andmodifications. For example, the blackened film 82 may be formed only inthe active area Aa1. Alternatively, it is possible to provide anadditional step to remove the blackened layer 62 produced in thenon-active area Aa2, especially those portions of the blackened layer 62which connect with an external wire such as FPC. It is also possible touse a method in which after forming the metal layer 61 of the electrodes40 by patterning of the metal film 81, a blackened layer 62 is producedon the metal layer 61.

<<<Technical Effects>>>

In the above-described embodiment, the detection electrodes 50 includethe conductive meshes 55 in which the thin conductive wires 60 arearranged in a mesh pattern that defines the large number of open areas71. The height of the thin conductive wires 60 of the conductive meshes55 may be not less than 0.2 μm and not more than 2 μm, and the width Wof the thin conductive wires 60 may be not less than 1 μm and not morethan 5 μm. The thin conductive wires 60 of the conductive meshes 55 eachhave a base surface 66 on the substrate 35 side, a flat top surface 67located opposite to the base surface 66, and a pair of side surfaces 68extending between the base surface 66 and the top surface 67. Accordingto the thin conductive wires 60 having such cross-sectional dimensionsand shape, the thin conductive wires 60, constituting the electrodes 40of the touch panel sensor 30, can be thinned while maintaining theelectrodes 40 at a low resistance. The thinned thin conductive wires 60,even in combination with high-definition pixels or with short-pitchpixels provided in a portable terminal, called a tablet, can achieve ahigh detection accuracy while sufficiently making the detectionelectrodes 50 invisible.

In the above-described embodiment, the substrate 35 preferably hasin-plane birefringence with a retardation Re of not less than 6000 nm.The use of such a substrate 35 can effectively obscure a rainbow patterneven when image light from the image display mechanism 12 is aparticular polarization component.

In the above-described embodiment, the thin conductive wires 60constituting each conductive mesh 55 are composed of the large number ofboundary segments 73 each extending between two branch points 72 andwhich define the open areas 71, the average of the number of boundarysegments 73 extending from each branch point 72 is not less than 3.0 andless than 4.0 and, in addition, there exists no direction in which openareas 71 are arranged at a constant pitch, i.e. at a constant repeatingpitch. The use of such conductive meshes 55 can effectively obscuremoire which can be produced when the touch panel sensor 30 having theconductive meshes 55 is superimposed on the image display mechanism 12in which pixels P are arranged regularly (periodically), or moire whichcan be produced when the touch panel sensor 30 is superimposed onanother touch panel sensor 30 and, at the same time, can effectivelyobscure a dark/light pattern in the conductive meshes 55.

In the above-described embodiment, the thin conductive wires 60constituting each conductive mesh 55 are composed of the large number ofboundary segments 73 each extending between two branch points 72 andwhich define the open areas 71, and, of the open areas 71 contained ineach conductive mesh 55, those open areas 71 which are surrounded by 6boundary segments 73 are contained most. The use of such conductivemeshes 55 can effectively obscure moire which can be produced when thetouch panel sensor 30 having the conductive meshes 55 is superimposed onthe image display mechanism 12 in which pixels P are arranged regularly(periodically), or moire which can be produced when the touch panelsensor 30 is superimposed on another touch panel sensor 30 and, at thesame time, can effectively obscure a dark/light pattern in theconductive meshes 55.

<<<Variations>>>

Various changes and modifications may be made to the above-describedembodiment. Some exemplary variations will now be described withreference to the relevant drawings. In the following description andrelevant drawings, the same reference numerals are used for the samemembers or elements as used in the above-described embodiment, and aduplicate description thereof will be omitted.

As well shown in FIGS. 2 and 4, in the first touch panel sensor 31 andthe second touch panel sensor 32 of the above-described embodiment, theelectrodes 40 are formed on the viewer-side surface of the substrate 35.However, the electrodes 40 may be formed on the image display mechanism12-side surface of the substrate 35 in at least one of the first touchpanel sensor 31 and the second touch panel sensor 32.

In the embodiment illustrated in FIG. 15, the electrodes 40 are providedon the image display mechanism 12-side surface of the substrate 35 inboth of the first touch panel sensor 31 and the second touch panelsensor 32. In the embodiment illustrated in FIG. 15, the laminate 20 aof the touch panel device 20 is composed of a cover layer 28, anadhesive layer 25, the first touch panel sensor 31, an adhesive layer24, the second touch panel sensor 32, an adhesive layer 26, a supportlayer 27, and a low-refractive index layer 23, arranged in this orderfrom the viewer side, i.e. from the opposite side from the image displaymechanism 12.

FIG. 16 shows an example of the touch panel sensor 30 which can beincorporated into the touch panel device 20 of FIG. 15. The touch panelsensor 30 shown in FIG. 16 comprises a substrate 35 and electrodes 40provided on the substrate 35. The electrodes 40 each comprise ablackened layer 62 located on the substrate 35 side and having a basesurface 66, and a metal layer 61 provided on the blackened layer 62 andhaving a top surface 67. Thus, also in the embodiment illustrated inFIG. 16, the blackened layer 62 is disposed on the viewer side of themetal layer 61 as in the above-described embodiment. The electrodes 40shown in FIG. 16 differ from the electrodes 40 of the above-describedembodiment in the order of lamination of the metal layer 61 and theblackened layer 62 onto the substrate 35, and can otherwise have thesame construction as the electrodes 40 of the above-describedembodiment. The blackened layer 62 and the metal layer 61, shown in FIG.16, can be produced by the various methods described above. For example,the blackened layer 62 can be produced from a nickel or chromium filmwhich has been formed by sputtering on the substrate 35. Alternatively,the blackened layer 62 can be produced from a coating, containing a dyeor a pigment, applied to the substrate 35.

In the above-described embodiment, the shape of each electrode 40 in across-section along the thickness direction, in particular the shape ofeach thin conductive wire 60 of a conductive mesh 55 in a cross-sectionalong the thickness direction, is tapered in a direction from the basesurface 66 toward the top surface 67; however, the present invention isnot limited to such a construction. For example, as shown in FIG. 17,the cross-sectional shape of each electrode 40, particularly thecross-sectional shape of each thin conductive wire 60 may be taperedsuch that the width W₂ at the top surface 67 is wider than the width W₁at the base surface 66. Particularly in the embodiment illustrated inFIG. 17, the width of each thin conductive wire 60 changes such that itsolely decreases in a direction from the top surface 67 toward the basesurface 66, in other words, in a direction toward the image displaymechanism 12. In particular, in the embodiment illustrated in FIG. 17,the width of each thin conductive wire 60 continuously decreases in adirection from the top surface 67 toward the base surface 66, in otherwords, in a direction toward the image display mechanism 12. When thetouch panel sensor 30 is incorporated into the display device 10 and thetouch panel device 20 such that the top surface 67 faces the viewer asshown in FIG. 17, the blackened layer 62, disposed nearer to the viewerthan the metal layer 61, can make the metal layer 61 more invisible.This makes it possible to enhance image contrast, thereby improving thevisibility of images displayed by the image display mechanism 12.

From the viewpoint of making the metal layer 61 less visible by theblackened layer 62 and thereby enhancing image contrast, the width ofeach electrode 40 (thin conductive wire 60) need not change such that itsolely decreases in a direction from the top surface 67 toward the basesurface 66, in other words, in a direction toward the image displaymechanism 12. Further, the width of each electrode 40 (thin conductivewire 60) need not continuously decrease in a direction from the topsurface 67 toward the base surface 66, in other words, in a directiontoward the image display mechanism 12. The metal layer 61 can be madeless visible by the blackened layer 62 and image contrast can beenhanced also in the case where the width of each electrode 40 (thinconductive wire 60) first changes such that it solely decreases in adirection from the top surface 67 toward the base surface 66, and thenchanges such that it increases in a direction from the top surface 67toward the base surface 66, i.e. in the case where the cross-sectionalshape of each electrode 40 (thin conductive wire 60) is inverselytapered only in the vicinity of the top surface 67. Further, the metallayer 61 can be made less visible by the blackened layer 62 and imagecontrast can be enhanced also in the case where the width of eachelectrode 40 (thin conductive wire 60) first changes such that it solelyincreases in a direction from the top surface 67 toward the base surface66, and then changes such that it decreases in a direction from the topsurface 67 toward the base surface 66, i.e. in the case where thecross-sectional shape of each electrode 40 (thin conductive wire 60) isinversely tapered only in the vicinity of the base surface 66.

It has been found in the present inventors' studies that the width W₂ atthe top surface 67, the width W₁ at the base surface 66, and the heightH of the top surface 67 from the base surface 66 preferably satisfy thefollowing relational expression:1≦H/((W ₂ −W ₁)/2)≦2

If H/((W₂−W₁)/2) is less than 1, the adhesion of the electrodes 40 tothe substrate 35 can be insufficient because of too large tapering ofeach electrode 40. It is therefore possible that, depending on theconditions under which the touch panel sensor 30 is used, anelectrode(s) 40 may peel off from the substrate 35 and, in some cases,may be broken. On the other hand, if H/((W₂−W₁)/2) exceeds 2, there maybe an appreciable lowering of image contrast due to reflection of lightfrom the side surfaces 68.

Inversely tapered electrodes 40 can be produced by using a metal oxidefor the blackened film 82 in the production method described above withreference to FIG. 14: the blackened film 82 composed of a metal oxide isformed on the metal film 81, and the metal film 81 and the blackenedfilm 82 are subjected to etching using the patterned resist film 83 as amask. In general, compared to the metal film 81 composed of a metalmaterial, the blackened film 82 composed of an oxide of the metalmaterial is less eroded by etching. Accordingly, lateral erosion by sideetching progresses more in the metal film 81 than in the blackened film82. Further, lateral erosion by side etching in the metal film 81progresses more in a region distant from the blackened film 82 and nearthe substrate 35 than in a region rear the blackened film 82. Therefore,the inversely tapered electrodes 40 shown in FIG. 17 can be produced byadjusting the etching time.

FIG. 22 shows an exemplary inversely tapered electrode 40. FIG. 22 is ascanning electron microscopy (SEM) micrograph of a cross-section of theelectrode. In the micrograph shown in FIG. 22, gold is vapor-depositedon the surface of the electrode 40 and on part of the surface of thesubstrate. The vapor-deposited gold layer is provided on the sampletouch panel sensor for the sake of cross-sectional observation of theelectrode by SEM, and thus is not a constituent element of the touchpanel sensor.

While an exemplary mesh pattern of each conductive mesh 55, which isvery effective for preventing moire and a dark/light pattern, has beendescribed above, the mesh pattern of each conductive mesh 55 is notlimited to the above-described exemplary one. Instead of theabove-described construction, any known technique for preventing moireand a dark/light pattern may be appropriately applied to the conductivemeshes 55. Moire and a dark/light pattern can be less visible dependingon the width of the thin conductive wire 60 of each conductive mesh 55,the area of each conductive mesh 55, etc. Therefore, the thin conductivewires 60 of each conductive mesh 55 may be arranged not in theabove-describe mesh pattern of each conductive mesh 55 but in a squarelattice arrangement, a honeycomb arrangement, or the like.

Though in the above-described embodiment the detection electrodes 50 arecomposed of the connecting wires 51 and the conductive meshes 55, thepresent invention is not limited to such detection electrodes 55. Forexample, as shown in FIG. 18, each detection electrode 50 may consist ofa single conductive mesh 55 formed in an elongated area. In theembodiment illustrated in FIG. 18, the detection electrodes 50 arecomposed of a large number of conductive meshes 55 formed instripe-shaped areas, and the extraction electrodes 45 are composed ofextraction wires 46 connected to the conductive meshes 55.

Though in the above-described embodiment the projection capacitancetouch panel device 20 comprises the first touch panel sensor 31 and thesecond touch panel sensor 32, the present invention is not limited tosuch a touch panel sensor. For example, as in the touch panel sensor 30shown in FIG. 19, conductive meshes 55 may be formed intwo-dimensionally arranged areas in an active area Aa1 defined on asubstrate 35.

In the embodiment illustrated in FIG. 19, each conductive mesh 55 isconnected via a connecting wire 51 to a corresponding extraction wire46. In the embodiment illustrated in FIG. 20, a single conductive mesh55 is formed in the entire area of an active area Aa1 defined on asubstrate 35. The conductive mesh 55, from the four corners, isconnected to extraction wires 46. Thus, the touch panel sensor 30 shownin FIG. 19 constitutes a surface capacitance touch panel.

The modifications described above can of course be made in anappropriate combination to the above-described embodiment.

The invention claimed is:
 1. A touch panel sensor comprising: asubstrate; and an electrode provided on the substrate and having adetection electrode for use in positional detection and an extractionelectrode connected to the detection electrode, wherein the electrode,in any cross-section thereof in a thickness direction, includes a metallayer which occupies at least part of the cross-section, wherein themetal layer of the detection electrode and the metal layer of theextraction electrode are formed integrally at a joint between thedetection electrode and the extraction electrode, wherein the detectionelectrode includes a conductive mesh having a conductive wire which isarranged in a mesh pattern that defines open areas, the conductive wirehaving a height of not less than 0.2 μm and not more than 2 μm and awidth of not less than 1 μm and not more than 5 μm, wherein theconductive wire of the conductive mesh have a base surface on thesubstrate side, a flat top surface located opposite to the base surface,and a pair of side surfaces extending between the base surface and thetop surface, and wherein the conductive wire of the conductive meshfurther includes a blackened layer provided on the opposite side of themetal layer from the substrate and forming the top surface.
 2. A touchpanel sensor comprising: a substrate; and an electrode provided on thesubstrate and having a detection electrode for use in positionaldetection and an extraction electrode connected to the detectionelectrode, wherein the electrode, in any cross-section thereof in athickness direction, includes a metal layer which occupies at least partof the cross-section, wherein the metal layer of the detection electrodeand the metal layer of the extraction electrode are formed integrally ata joint between the detection electrode and the extraction electrode,wherein the detection electrode includes a conductive mesh having aconductive wire which is arranged in a mesh pattern that defines openareas, the conductive wire having a height of not less than 0.2 μm andnot more than 2 μm and a width of not less than 1 μm and not more than 5μm, wherein the conductive wire of the conductive mesh have a basesurface on the substrate side, a flat top surface located opposite tothe base surface, and a pair of side surfaces extending between the basesurface and the top surface, and wherein the conductive wire of theconductive mesh further includes a blackened layer provided on thesubstrate side of the metal layer and forming the base surface.
 3. Thetouch panel sensor according to claim 1, wherein the width of theconductive wire of the conductive mesh changes such that it solelydecreases in a direction from the top surface toward the base surface.4. The touch panel sensor according to claim 1, wherein the width of theconductive wire of the conductive mesh first changes such that it solelydecreases in a direction from the top surface toward the base surface,and then changes such that it solely increases in a direction from thetop surface toward the base surface.
 5. The touch panel sensor accordingto claim 1, wherein the mesh pattern has a large number of boundarysegments each extending between two branch points, and the boundarysegments define the open areas; and wherein, in the mesh pattern, theaverage of the number of boundary segments extending from each branchpoint is not less than 3.0 and less than 4.0, and there exists nodirection in which open areas are arranged at a constant pitch.
 6. Thetouch panel sensor according to claim 5, wherein the average of thenumber of boundary segments connected at each branch point is more than3.0.
 7. The touch panel sensor according to claim 5, wherein the averageof the number of boundary segments connected at each branch point is3.0.
 8. The touch panel sensor according to claim 1, wherein the meshpattern has a large number of boundary segments each extending betweentwo branch points, and the boundary segments define the open areas, and,wherein, of the open areas contained in the mesh pattern, those openareas which are surrounded by 6 boundary segments are contained most. 9.The touch panel sensor according to claim 8, wherein the average of thenumber of boundary segments connected at each branch point is more than3.0.
 10. The touch panel sensor according to claim 8, wherein theaverage of the number of boundary segments connected at each branchpoint is 3.0.
 11. A touch panel device comprising the touch panel sensoraccording to claim
 1. 12. A display device comprising the touch panelsensor according to claim
 1. 13. A display device comprising the touchpanel device according to claim
 11. 14. The touch panel sensor accordingto claim 2, wherein the width of the conductive wire of the conductivemesh changes such that it solely decreases in a direction from the topsurface toward the base surface.
 15. The touch panel sensor according toclaim 2, wherein the width of the conductive wire of the conductive meshfirst changes such that it solely decreases in a direction from the topsurface toward the base surface, and then changes such that it solelyincreases in a direction from the top surface toward the base surface.16. The touch panel sensor according to claim 2, wherein the meshpattern has a large number of boundary segments each extending betweentwo branch points, and the boundary segments define the open areas; andwherein, in the mesh pattern, the average of the number of boundarysegments extending from each branch point is not less than 3.0 and lessthan 4.0, and there exists no direction in which open areas are arrangedat a constant pitch.
 17. The touch panel sensor according to claim 2,wherein the mesh pattern has a large number of boundary segments eachextending between two branch points, and the boundary segments definethe open areas, and, wherein, of the open areas contained in the meshpattern, those open areas which are surrounded by 6 boundary segmentsare contained most.
 18. A touch panel device comprising the touch panelsensor according to claim 2.